This invention relates to improvements in aircraft design configuration and related operational functions primarily in the supersonic flight regimes (Mach I and above).
Until the present, conventional, tapering, conical boattail shapes generally formed the afterbody of aircraft. A typical afterbody of the known art is illustrated in U.S. Pat. No. 3,447,761 and also in U.S. Pat. No. 3,076,625. Several disadvantages are inherent in the conventional conical boattail shapes, especially when the engines are buried, or housed within the fuselage afterbody, forming bulky, aerodynamically inefficient, postern profiles and particularly between engines in multi-engine aircraft. The aerodynamic problems associated with the postern profile of conventional aircraft are especially deleterious and complex in the supersonic speed regimes. The problem is even more severe if the nozzles of the buried engines emerge from the fuselage. At supersonic speeds flow separation occurring from the aft fuselage surface contours and the highly converging surfaces between the emerging engine nozzles increases the postern of wake drag of the aircraft and is significantly detrimental to its performance. This base drag, induced by the conical boat-stern-like aft end of a conventional fuselage, is very detrimental to the performance of aircraft, particularly during supersonic flight.
High fineness ratio which is derived by dividing the length of the fuselage by its maximum equivalent diameter presently necessitates use of exceptionally long fuselages which are required in order to reduce the conical boatstern drag effect at transonic and supersonic speeds. Complete elimination of such base drag is a highly sought for objective by those skilled in the art of designing high performance aircraft. Additional lengthening of the fuselage for the purpose of achieving a high fineness ratio is not feasible since increased wetted area drag results therefrom. Wetted area drag is also detrimental to the achievement of efficient transonic and supersonic performance as is trim drag induced by conventional devices for the necessary trimming out the airplane against pitching moment.